THE VITAL PHENOMENA OF BACTERIA. 59 



introduction of hydrogen, the bacterium ap- 

 proached the edge of the drop ; if the tension 

 was raised by the introduction of oxygen, it 

 drew away from the edge. If the oxygen 

 is removed, not mechanically, but by the re- 

 placement of the air by other gases, it is found 

 that carbon dioxide and sulphuretted hydro- 

 gen are poisons for bacteria, while hydrogen 

 seems to have no effect on them. In the fer- 

 mentation industry it was known long ago 

 that the must could be " aerated " with hy- 

 drogen, and that, therefore, not the addition 

 of oxygen, but the removal of carbon dioxide 

 was the important part of the process. 



The facts of anaerobiosis are of great im- 

 portance to technical biology and to pathology. 

 Since, under strictly anaerobiotic conditions, 

 any secondary oxidation of the primary decom- 

 position products is impossible, the latter accu- 

 mulate without formation of bye-products. In 

 the technique of fermentation this fact enters 

 into consideration in the so-called " bottom fer- 

 mentation." In disease, the possibility of ex- 

 tracting physically bound oxygen from the blood 

 plasma is of only secondary importance ; other- 

 wise all individuals who suffer from invasion of 

 the blood by microscopic organisms, would die 

 from carbonic acid poisoning. Formation of 

 carbonic acid, however, may, as a symptom of 



